1. Field of the Invention
This invention relates to polyamide polymers and is more particularly concerned with novel polyamides having a ketene-aminal as a recurring unit in the polymer chain and the novel preparation of said polyamides.
2. Description of the Prior Art
Various types of polyamide polymers are known to those skilled in the art, see for example The Encyclopedia of Polymer Science and Technology, Vol. 10, pp 347-593, 1969, Interscience Publishers, New York, N.Y. The various kinds of recurring units disclosed therein all share the common feature of being linked by the recurring carbonamide group ##STR2##
Clemens et al (J. of Organic Chem. 29, 2932 [1964]) have reported the formation of monoamides and diamides of a ketene-aminal by the reactions of 1,1-di(1-piperidinyl)ethylene with 1 and 2 moles respectively of alkyl or aryl monoisocyanates. The objective of this reported work was the study of the nuclear magnetic resonance spectra of the various amide ketene-aminals and their corresponding amidinium salts formed by the reaction of the ketene-aminals with acids.
We have now discovered a novel class of thermoplastic polyketene-aminal based polyamides defined below wherein the ketene-aminal grouping is a regular recurring part of the polymer backbone.
The polyamides in accordance with the present invention are easily prepared by a novel direct condensation polymerization process wherein no by-products are produced.
Unexpectedly, the polymerization can be effected under very mild conditions but, even more unexpectedly, the polymerization occurs very rapidly to offer one of the fastest, if not the fastest, means for preparing a polymer having carbonamide linkages.